Hi David, welcome to the forum and the world of Boxstering!
First, your questions have been answered many times on this forum. Please do a search to get all kinds of info.
Having said that, I'd change the oil right away if I had no idea when the last change was done. And change it every 5k miles (one summer driving season for me).
There is debate
about using M1 oil. Many, including me, don't think it's the most cost effective oil available. (I use Castrol Syntec/Edge 5/40, only because I can't get 10/40.)
Consider getting the spin on oil filter adaptor, rather than using the stock oil filter setup. This avoids the potential for bypassing oil filtration, which is inherent in the stock filter canister. If you want to stick with the stock filter setup, use Wix/ Napa Gold. Fleetfilter is a good source.
To go the full mile, some are using magnets on their filter canisters as well.